1. Field of the Invention
The present invention relates in general to a system and method for the detection of freefall with spin in portable electronic devices, in order to protect the hard disk drive or other sensitive components of such devices from damage due to impact.
2. Description of the Background Art
In recent years, the demand for portable electronic devices such as the notebook computer, PDA, MP3 player, digital camera, and mobile phone has increased significantly. As the use of portable electronic devices with always-on onboard memory or hard disk drives (HDD) increases, so does the risk of lost data due to physical impact of the devices when they are accidentally dropped. Data loss and its resulting loss in productivity have the potential to cause personal inconvenience, lost communications, reduced productivity and in more catastrophic cases, irretrievably lost data that could result in serious personal, family or business organization consequences.
To address the foregoing problem, freefall protection systems have been devised that can detect simple freefall of these portable devices and act to park the read/write head of the onboard memory or HDD prior to impact. However, while this current technology is able to detect acceleration changes in one-dimension, this same technology is not capable of accurately detecting the very common scenario associated with a dropped object that is experiencing “spin” (the revolution or tumbling of the object, as it falls).
An accelerometer at rest measures 1 G (gravity) of acceleration. An accelerometer will measure 0 G of acceleration in simple free fall, no matter the fall direction. However, there are problems associated with detecting the acceleration of an object with spin, which include the following. If an object is dropped with a spin of approximately 4 revolutions per second, an accurate and more likely real-life scenario, the accelerometer never approaches 0 G throughout the entire fall. Rather, the accelerometer will measure over 3.0 G during much of the fall as the spin causes centrifugal and centripetal acceleration to be placed on the object. In such a scenario, a conventional freefall system arrangement using a single tri-axis accelerometer with a high-G threshold will be useless in detecting the fall.
A further issue arises when portable electronics are being used in everyday activity, such as jogging or dancing, which may cause false detection of a falling event. The mobile device market is therefore in need, more then ever, for more reliable and accurate detection technology, for high-end protects in particular, that can distinguish between normal every day events and a fall prior to a potentially catastrophic impact.